1. Field of the Invention
The present invention relates to a method for producing food and beverage products with a high content of γ-aminobutyric acid and more specifically, relates to a method for producing food and beverage products containing a high concentration of γ-aminobutyric acid without adding glutamic acid or salts thereof, and food and beverage products with a high content of γ-aminobutyric acid.
Priority is claimed on Japanese Patent Application No. 2005-251213, filed Aug. 31, 2005, the content of which is incorporated herein by reference.
2. Description of the Related Art
γ-Aminobutyric acid is a nonprotein amino acid widely distributed in the living world and it is known to function as an inhibitory neurotransmitter in higher animals (non-patent document 1). Moreover, γ-aminobutyric acid is now known to have various physiological functions, and hypotensive effects (non-patent document 2), brain function improving effects (non-patent document 3), ataractic effects (non-patent document 4), and the like have been reported.
Although γ-aminobutyric acid is one of the natural amino acids contained in food products such as brown rice, beni-koji, tea, and certain vegetables and fruits, only trace amounts thereof are present in these foods and there have been no food products containing an effective dose for expressing the original physiological functions thereof (non-patent document 4). Various methods to increase the content of γ-aminobutyric acid in food products have been studied and techniques such as those below are known.
(i) Production method of food and beverage products characterized in that glutamic acid contained in the processed products of ripe tomatoes is partially converted to γ-aminobutyric acid by allowing glutamic acid decarboxylase to act on the processed products of ripe tomatoes (patent document 1). (ii) Production method of tomato beverages characterized in that tomatoes or tomatoes and other vegetables and/or fruits are placed in oxygen-free atmosphere and are crushed and squeezed after glutamic acid contained in them has been partially converted to γ-aminobutyric acid (patent document 2). (iii) Production method of food and beverage products or seasoning products, with high content of γ-aminobutyric acid fermented by lactic acid bacteria characterized in that fermentation by lactic acid bacteria is carried out by adding glutamic acid or materials containing glutamic acid and strains of lactic acid bacteria with γ-aminobutyric acid-producing capability to ingredients of food and beverage products or seasoning products (patent document 3).    [non-patent document 1] Seibutsu Kogaku Kaishi 75, 239-244, 1997    [non-patent document 2] Japanese Pharmacology & Therapeutics (Yakuri to Chiryou) 28, 529-533, 2000    [non-patent document 3] up-to-date food processing (Shokuhin to Kaihatsu) Vol. 36, No. 6, 4-6, 2001    [non-patent document 4] Journal of the Japanese Society of Food Science and Technology (Nippon Shokuhin Kagaku Kogaku Kaishi) 47, 596-603, 2000    [patent document 1] Japanese Unexamined Patent Application, First Publication No. Hei 3-224467    [patent document 2] Japanese Unexamined Patent Application, First Publication No. Hei 4-51878    [patent document 3] Japanese Laid-Open Patent Application No. 2004-215529
However, with the techniques described in patent document 1, there have been problems such as a low conversion efficiency to γ-aminobutyric acid of approximately 40% at most (Example 2), and also difficulties in adding enzyme sources aseptically resulting in a high risk of bacterial and/or fungal contamination during conversion of glutamic acid to γ-aminobutyric acid. With the techniques described in patent document 2, glutamic acid is converted to γ-aminobutyric acid in tomatoes due to changes in the metabolic pathways when the tomatoes are placed under oxygen-free conditions. However, likewise, there have also been problems such as a low conversion efficiency of approximately 40% (Example 6), and also difficulties in providing oxygen-free conditions aseptically resulting in a high risk of bacterial and/or fungal contamination during conversion of glutamic acid to γ-aminobutyric acid. With the techniques described in patent document 3, since fermentation does not take place without the addition of glutamic acid to produce γ-aminobutyric acid, there have been economic problems and unfavorable labeling of ingredient statements.